The invention relates to a perfect binder used for processing book blocks, wherein the binder comprises a conveying device with a closed circular path for conveying the book blocks. A number of successively following processing stations are assigned to the conveying device, wherein the conveying device furthermore is provided with a number of clamping devices for respectively conveying one book block to the processing stations and wherein one of the processing stations is embodied for processing the book block spine. The invention furthermore relates to a corresponding perfect binding method.
For hardcover book production, book binderies are increasingly confronted with the task of having to produce smaller book block series, frequently involving only one copy of a book. For that reason, printing machines requiring short retooling times are generally used for printing the content of these books. Short runs are most often produced with digital printers, which make it possible to dynamically change the printing content, thus making it possible to sequentially print the pages of a book and then process these further into a book block. In most cases, this is done in-line, meaning the required processing steps starting with the printing, the folding and collating of the printed sheets, the perfect binding, all the way to the finishing of the bound book, are successive, and are realized in the same system, which is also called a book-binding line.
During a perfect binding operation, the individual sheets and/or signatures previously gathered into a book block are processed through milling along the spine, which is followed by applying adhesive along the spine. A casing is then pressed against the spine, such that the casing and the book block spine are glued together. If a flexible casing is used, then the finished product is called a perfect-bound softcover. If a rigid casing is used, the finished product is referred to as a perfect-bound hardcover.
For hardcover book production, the book block is provided with end sheets that are glued with the aid of a thin bead of glue onto both sides of the book block. In the finished book, these end sheets function as hinges to the casing. To be able to align the end sheets cleanly and flush with the book block spine, they are advantageously supplied only after the milling operation. A backing strip is then attached to the book block spine, such that it overlaps the spine, for example with the aid of hot glue or PUR (polyurethane reactive adhesive). The backing strip applied in this way ensures that the book block is held together. In the following step, the book block is then trimmed to the specified format and a hardcover is attached with adhesive to the two end sheets.
A perfect binder with a compact design is known from the Swiss patent document CH 325096. The perfect binder includes a conveying device having a closed circulating path, and processing stations arranged in the region of the circulating path. The conveying device is embodied as a rotating table with gripper holders arranged along the periphery, in which respectively one pair of clamping jaws is positioned which holds the book block. Owing to the fact that the clamping jaws hold the book block throughout the processing operation, the end sheets must be supplied to the perfect binder jointly with the book block, meaning prior to the milling of the back, which causes the above-mentioned quality problems.
European patent document EP 1344655 A2 discloses a perfect binder, especially suited for short runs, with the feed station arranged downstream of the milling device. The system disclosed therein is a linear, relatively long system. It includes several processing stations arranged successively in a row, with intermittent book block conveying, which is realized with a back-and-forth moving conveying device. In the process, the book block is conveyed while positioned on its spine, and is gripped in the lower region on both sides by a clamping bar. The clamping bar is part of the conveying device, and transports the book block through the milling device and into the feed unit for the end sheets. Once there, the book block is transferred to a holding clamp, which grips the book block in the center region. Immediately thereafter, the clamping bars are released and the end sheets, as well as the backing strip, are supplied to the book block. The two clamping bars meanwhile return to the starting position to take over the next book block. As the next book block is supplied, a back region of the clamping bars takes over conveying the book block that was previously provided with the end sheets and backing strip, so as to transport it to the following processing station.
The above-described return movement of the clamping bars, however, is slower than the movement for feeding the end sheets and the backing strip, meaning the book block processed in this station is ready for the further processing before the clamping bars have reached the starting position. As a result of the back-and-forth movement of the conveying device, the cycle time of the perfect binder is therefore extended unnecessarily.
The clamping bars furthermore press together the book block near the spine, and thus compress it in the lower region. In the unit for feeding the end sheets, the book block, which is loose in the upper region, is gripped by the holding clamp while the clamping bars are still engaged. The clamping bars subsequently opened up to clear the way for supplying the end sheets. Being encircled by the clamping device unsettles the book block and can result in inaccuracies and displacements. For example, a voluminous book block must be squeezed or compressed thoroughly because the air trapped inside the book block must first be allowed to escape. In the process, the previously created milling surface can be damaged, thereby leading to problems with the adhesive application and thus the quality of the final product. A relatively high technical expenditure is furthermore required to achieve the necessary precision during the above-described transfer of the book block from the conveying device to the holding clamp. Finally, the end sheets can be supplied to the book block only during a phase where the system is stopped.